Projecting the Impact of Climate Change on Coldwater Stream Temperatures in Minnesota Using Equilibrium Tmperature models

Water temperature is a very important characteristic of aquatic habitats, particularly those supporting coldwater fish species such as trout [Eaton et al. 1995]. Stream temperature not only controls the survival of juvenile and adult coldwater fish, but also affects their reproduction and food sources such as macroinvertebrates [Durance and Ormerod 2007]. Hydrogeologic and climate settings constrain the existence of coldwater streams. In Minnesota, for example, trout streams are created by (1) karst springs in the southeast region of the state, near Rochester, 2) by cold wetlands in the northeast region of the state, near Duluth, and 3) by shallow groundwater aquifers in other regions of the state. The hydrological and climatological processes that maintain coldwater stream habitat vary between these regions, but involve a combination of cold water sources from groundwater or wetlands, riparian shading, and/or temperate climate. In other regions of the USA and the world, alpine settings with coldwater sources from snow or ice and cold mountain climate provide another important category of trout streams [Brown and Hannah 2007; Clark et al. 2001; Hari et al. 2006].